I use 12.16. I might have been mistaken in thinking that I have to delete them in the browser "Preferences" before CCleaner destroys them. CCleaner gives you the option to exempt cookies you want to keep. I think I used to do it that way but forgot. Thanks for reminding me.

In Opera 11x-12.x browsers, you can delete all "new" cookies upon exit, via ctrl+F12 > Advanced > Cookies > check: "delete new cookies when exiting Opera" > OK. So, where you want to exempt certain cookies like log-ins, etc, but delete everything else, the trick is to:
1) clear all the cookies entirely from within Opera, then uncheck the "delete new cookies" setting box as located above, then exit Opera
2) restart Opera, visit and log in only to each site whose cookies you want preserved, then exit Opera
3) Again restart Opera and check the "delete new cookies" setting box
The object is to create within Opera only those cookies that you want preserved and leave them in place. Restarting Opera causes previously-created cookies to become "old" cookies, hence any future auto-deletion of "new" cookies upon exiting Opera will clear everything out except the "old", desired cookies. I've been using this technique for years with Opera, and it works fine - though it is admittedly a bit obscure of a method.

Of course, some site log-in cookies expire at a certain point (this site being one), so you may have to re-log-in later again. But that will merely update the appropriate, existing cookies and renew them, so you won't have to repeat all the above steps.

I'd tread very lightly with CCleaner. If you allow it to clean your files without examining what it is removing, you're asking for trouble. And whatever you do, don't allow it to mess with your registry.

I agree with Leushino. I use CCleaner on occasion, but I do so with great caution and reserve. In some cases, entries it finds are clearly marked and are safe to remove... but in other cases, the terms/titles/descriptions are either obscure or misleading (through no fault of CCleaner), and removal can do some real damage. It's a powerful tool, but like anything with great power, it must be used carefully. Many users are tempted to just turn it loose, throwing caution to the wind... and if it trashes the registry as a result, things can and do get very, very ugly - very quickly.

@leushino, @blackbird71: Thanks for the stern warning. Your advice to tread very lightly with great caution and appreciating its great power just sent me chills. Im going to be re-examining everything I do with CCleaner again. I have been using the registry cleaner on it for years. Im going to stop now. I shouldnt let a program that isnt specially made to clean the registry to do things with it. Shivers.